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Would a heavier front sway bar w/urethane bushings make a huge difference?
Or would I need to install urethane in the entire front end?
I didn't see any threads on this for the 420. I should check under S-Type - is the same, right?
Looking for much flatter cornering.
Same as S Type. Urethane bushes are noisy & spoil the ride. (only Potassium Borate containing greases shut them up from squeaking if you go anywhere near dust ~ Good luck finding less than a 180Kg drum). Fit a rear sway bar/anti roll bar like an E Type. All the mounting points are there with plugs in them ~ the bar is just wider on a 420. Let me see if I can find the supplier. A stiffer front bar will also help. Bushes make little difference to body roll or flatter cornering. JCS on the S Type Register is the rear roll bar specialist.
The roll on these cars looks worse externally than from behind the drivers wheel.
I hate Polyurethane bushes ~ they are crap & increase NVH. They don't belong on a road car. Racing is a different matter where you don't care about NVH.
E Type Rear Suspension
Half an E Type suspension showing full roll bar. They are complex.
Last edited by Glyn M Ruck; 07-02-2023 at 08:21 PM.
If you are swaying that much in a corner then you are going too fast. Learn to drive smoother in a 1960s Jaguar rather than think you are in a 2023 Jaguar at the Nordschleife.
That said it could be that your Shock absorbers are shot rather than bushes and sway bar. How old are your shock absorbers? New shocks and springs would be my first go to.
I've no real experience of polyurethane bushes. They can be excellent in essentially static applications such as series XJ steering rack mounts. Poly suspension bushes come in different grades of stiffness and I understand the most flexible deforms like rubber rather than sliding. They may also be more flexible than rubber which must defeat the handling objective.
'Handling' is a vague and subjective quality. Is stiffer always better, that is faster? Don't be fooled by the traditional Jaguar compliance. They have often proved to be faster than supposedly better handling, but actually merely stiffer, rivals.
An anti-sway bar has two main effects. By reducing roll, it helps to keep the wheels (all four) closer to upright, thereby reducing slip angles and raising the limit of adhesion. However, it also changes the balance (for better or worse) between the front and rear of the car. For example, a bar at the rear increases weight transfer between wheels at the rear (and reduces it at the front). This increases slip and potentially reduces adhesion at the rear relative to the front, increasing oversteer. When you add bars, think about how the car behaves as standard and how it's balance might (not) be improved. For a 420, a bar at the rear will require another, or other changes, at the front.
Handling isn't only springs and sway bars. There's a lot of work that can be done especially on the front suspension with camber, castor and toe. All round, standard dampers tend to be on the soft side and changing them is a relatively easy upgrade. Finally, we shouldn't mistake worn out 60-year old parts for weakness in the original design.
There are several books worth reading: a reliable one is Vehicle Dynamics by Tom Gillespie. And be aware that the fact that a famous sports car designer or someone on an internet forum (I guess that includes me) writes something doesn't make it true.
Indeed Peter ~ My Alfa sedan's all used to lean/roll but did not let go & if they did at the extreme they did so gracefully & controllably. The Sprints & Spiders rolled less but still rolled. I only had 7 of them in a row. They handled superbly stock.
The HBE Harvey Bailey Engineering in the UK kit takes your concerns into account which is why it costs over 800 Pounds Sterling. It is properly engineered.
Meaningful changes to castor & camber on our cars is a major undertaking. It would cost a fortune. I'm talking > 9.6 degrees castor & 2 to 3 degrees of negative camber. My running of numerous racing teams in my career tells me this.
My experience of Poly bushes is they all suck unless on a racetrack with stiff ones that you change often ~ Never mind grade selected. In SA the softer ones always crack in our conditions.
I'm with you ~ trying to make these cars roll less can certainly lead to the unintended consequences of making the vehicle's handling worse. Changes of compliance in a vehicle is not a simple science.
Both Cass & you make a good point about adjustable shocks/coilovers. i.e. an adjustable version of what we have with the IRS already.
Last edited by Glyn M Ruck; 07-03-2023 at 07:16 AM.
They never installed a sway bar at the rear of the S-type or 420, for a reason.
They would break out way to quick, due to the heavy rear. Therefore they did not install them.
By the way I like the Poly bushes a lot, did not make the ride harsh.
Be aware different producers use different shore rates ( the lower the softer) A40 will be soft, A85 will be hard.
They never installed a sway bar at the rear of the S-type or 420, for a reason.
They would break out way to quick, due to the heavy rear. Therefore they did not install them.
By the way I like the Poly bushes a lot, did not make the ride harsh.
Be aware different producers use different shore rates ( the lower the softer) A40 will be soft, A85 will be hard.
Thank you so much! That is VERY helpful. I'm tragically unfamiliar with Jaguars. Finally, decades later, I wanted to learn more. So I bought this one.
I have no interest in my 'sports saloon' riding like my Imperial so don't mind, or almost prefer the harshness frankly.
It's 205 15s fill the wheel wells nicely and would never consider lower profiles, so I need the suspension to make up for it a little.
Same as S Type. Urethane bushes are noisy & spoil the ride. (only Potassium Borate containing greases shut them up from squeaking if you go anywhere near dust ~ Good luck finding less than a 180Kg drum). Fit a rear sway bar/anti roll bar like an E Type. All the mounting points are there with plugs in them ~ the bar is just wider on a 420. Let me see if I can find the supplier. A stiffer front bar will also help. Bushes make little difference to body roll or flatter cornering. JCS on the S Type Register is the rear roll bar specialist.
The roll on these cars looks worse externally than from behind the drivers wheel.
I hate Polyurethane bushes ~ they are crap & increase NVH. They don't belong on a road car. Racing is a different matter where you don't care about NVH.
I've no real experience of polyurethane bushes. They can be excellent in essentially static applications such as series XJ steering rack mounts. Poly suspension bushes come in different grades of stiffness and I understand the most flexible deforms like rubber rather than sliding. They may also be more flexible than rubber which must defeat the handling objective.
'Handling' is a vague and subjective quality. Is stiffer always better, that is faster? Don't be fooled by the traditional Jaguar compliance. They have often proved to be faster than supposedly better handling, but actually merely stiffer, rivals.
An anti-sway bar has two main effects. By reducing roll, it helps to keep the wheels (all four) closer to upright, thereby reducing slip angles and raising the limit of adhesion. However, it also changes the balance (for better or worse) between the front and rear of the car. For example, a bar at the rear increases weight transfer between wheels at the rear (and reduces it at the front). This increases slip and potentially reduces adhesion at the rear relative to the front, increasing oversteer. When you add bars, think about how the car behaves as standard and how it's balance might (not) be improved. For a 420, a bar at the rear will require another, or other changes, at the front.
Handling isn't only springs and sway bars. There's a lot of work that can be done especially on the front suspension with camber, castor and toe. All round, standard dampers tend to be on the soft side and changing them is a relatively easy upgrade. Finally, we shouldn't mistake worn out 60-year old parts for weakness in the original design.
There are several books worth reading: a reliable one is Vehicle Dynamics by Tom Gillespie. And be aware that the fact that a famous sports car designer or someone on an internet forum (I guess that includes me) writes something doesn't make it true.
Great. Your knowledge (& the knowledge here) is very helpful. I appreciate it! My shocks & springs seem great, but I haven't been able to fully wring this this out on the road too much. I kinda thought it would drive a little less boaty.
And btw I fairly certain the bushings are somewhat recent, but shall czech everything eventually.
Last edited by David Vincent; 07-03-2023 at 10:16 PM.
Great! ~ You can't go to a harder, less compliant bush without affecting NVH. It is an impossibility.
The HBE Harvey Bailey Engineering kit works very well on an S Type. Why the mounting points are provided by Jaguar. They were left off to save money. Why the E Type handles better.
When I restored my S Type many years ago I bought the Koni Classic shocks for the S Type. I should have stayed with the originals, as I find the ride bouncy and jiggly, even though the shocks are set to their softest setting. Springs are original, so that's not it. It's not the classic "magic carpet" ride that a an XJ6 or XJS delivers.
They never installed a sway bar at the rear of the S-type or 420, for a reason.
They would break out way to quick, due to the heavy rear. Therefore they did not install them.
I find that difficult to believe as the XJS has a rear bar (depending on year and market) and it's a heavier car and they do not have a tendency to break out the rear. My 6.0 XJS V12 has the sportpack with a 1" bar in the front and a 7/8" bar in the rear and it corners amazignly flat and stable. I can drive it hard through corners and it inspires confidence, it's not twitchy or slippery in the rear at all.
I suspect the reason the 420/ S Type didn't have a rear bar while the E Type did was simply the intended customer. Jaguar could save money by not fitting it to the saloons and the customers would never notice.
They never installed a sway bar at the rear of the S-type or 420, for a reason.
They would break out way to quick, due to the heavy rear. Therefore they did not install them.
By the way I like the Poly bushes a lot, did not make the ride harsh.
Be aware different producers use different shore rates ( the lower the softer) A40 will be soft, A85 will be hard.
That is simply not true. It was a cost saving measure. That's why all the mounting points exist. And they were intended as luxury cars where owners would not know or care.
I had all my spring rates reset to standard by the company that made the original springs for SA production. We were in Phase 2 of our local content program by then which was by weight. 53% of the weight of the vehicle had to be local. Why Lyons cleverly persuaded Govt. to accept blank blocks & heads from the UK and we machined and built the engines locally on the latest state of the art equipment for the era paid for by the SA taxpayer. Our engines were far more accurate than those built using the ancient junk that Browns Lane had mainly from Standard & the Daimler purchase. We only moved from weight to value at a later stage in the XJ6 era by which time Steelmobile were pressing the bodies as well. Something else they did better than Pressed Steel.
You can see my car in my signature
Last edited by Glyn M Ruck; 07-03-2023 at 09:55 PM.
When I restored my S Type many years ago I bought the Koni Classic shocks for the S Type. I should have stayed with the originals, as I find the ride bouncy and jiggly, even though the shocks are set to their softest setting. Springs are original, so that's not it. It's not the classic "magic carpet" ride that a an XJ6 or XJS delivers.
There seems to be a pretty good video (from what little I know!) about the S and the car has adjustables on it.
Personally I don't mind a little shallow bounce that goes with a more firm feel.
Watched this a few weeks back - gots to watch it again right now, since buying the 420...
The rear anti-roll bars are an interesting topic with a lot of history. For Heynes and Sayer, the E type was, at least originally, primarily a racing car to replace the D type. As such, a stiffer suspension with roll bars at both ends makes a lot of sense. Racing remained an interest after it became a production road car. Graham Hill did much of the testing for racing and he liked his cars close to rigid. Apart from the usual legacy factor in engineering, it's useful to have something that avoids the need for FIA homologation later.
As to the rear bar's effectiveness, many racers have removed or disconnected it, others haven't. It's a debate, a debate that continued to later models including the XJS. Norman Dewis recorded his discussions with Jim Randle on rear bars. According to Norman, it was settled by fitting a bar flexible enough to have no effect.
Now I'm going to speculate on the S type and 420 design. Knowing Bill Heynes' desire to produce GT versions, I'd suggest he chose to put the unused mountings in the rear suspension so that everything was ready for a car, probably a Mk2 GT with IRS, that would have used a small bar at the rear and a much stiffer bar at the front.
Given all that and knowing how they drive, if I were trying to make a S type or 420 corner flatter, I'd consider a rear bar, but only after fitting a much stiffer front bar. The HBE kit looks good and well thought out, but a heavy price for some bent rod. Anyone know a good blacksmith?
Yep ~ when a chap from the club said he was buying an HBE kit for over 800 GBP and then still had to get it here it made my eyes water. Although look at the price of a radiator today. I only paid 500 GBP for my uprated radiator at the time & thought that was steep.
Last edited by Glyn M Ruck; 07-04-2023 at 05:11 AM.
07-02-2023, 05:11 PM
